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ISSN Online: 2377-424X

ISBN Print: 978-1-56700-474-8

ISBN Online: 978-1-56700-473-1

International Heat Transfer Conference 16
August, 10-15, 2018, Beijing, China

EXPERIMENTAL EVALUATION OF THE FLOW BOILING HEAT TRANSFER COEFFICIENT OF DI-WATER INSIDE MINICHANNELS UNDER CONDITIONS CLOSE TO THE CRITICAL HEAT FLUX

Get access (open in a dialog) DOI: 10.1615/IHTC16.bae.021908
pages 647-652

要約

This work concerns an experimental evaluation of the flow boiling heat transfer coefficient of DI-water inside minichannels. Experiments were performed for mass velocities, G, from 133 to 600 kg/m2s, vapor qualities, x, up to 0.85 and heat fluxes, q, up to 2.5 MW/m2. For G<500 kg/m2s, the heat transfer coefficient initially decreases with increasing vapor quality, until achieves a minimum value. Then, its trend is shifted and the heat transfer coefficient increases as the vapor quality rises. Such behavior is explained based on the superposition of convective and nucleate boiling effects. For vapor qualities lower than the one corresponding to the minimum heat transfer coefficient (xmin), the heat transfer coefficient increases with increasing q and G. On the other hand, for q close to the CHF condition at the ending region of the test section and the heat transfer coefficient evaluated upstream to the CHF region decreases with increasing vapor quality. Comparisons among eight predictive methods and the experimental data were performed, none of the methods provided reasonable predictions of the present data. Therefore, taken into account this fact and considering that the methods for prediction of the heat transfer coefficient based on data for DI-water does not include in their database results for conditions close to the CHF, the empirical constants of the method of Kanizawa et al. [2] were modified based on the present database. The modified version of the method predicted more than 91% of its database within an error band of ±30% and provided a mean absolute error of only 12.1%.